For the photoconductive material to consitute a light receiving layer in a light receiving member for use in electrophotography, it is required to be highly sensitive, to have a high SN ratio [photocurrent (Ip)/dark current (Id)], to have absorption spectrum characteristics suited for the spectrum characteristics of an electromagnetic wave to be irradiated, to be quickly responsive and to have a desired dark resistance. It is also required to be not harmful to living things as well as man upon use.
Especially, in the case where it is the light receiving member to be applied in an electrophotographic machine for use in office, causing no pollution is indeed important.
From these standpoints, the public attention has been focused on light receiving members having a light receiving layer comprised of an amorphous material containing silicon atoms (hereinafter referred to as "A-Si"), for example, as disclosed in Offenlegungsschriftes Nos. 2746967 and 2855718 which disclose use of such light receiving member as an image-forming member in electrophotography.
For the conventional light receiving members having a light receiving layer comprised of A-Si material, there have been made improvements in their optical, electric and photoconductive characteristics such as dark resistance, photosensitivity, and photoresponsiveness, use-environmental characteristics, economic stability and durability.
However, there are still left subjects to make further improvements in their characteristics in the synthesis situation in order to make such light receiving member practically usable.
For example, in the case where such conventional light receiving member is employed as a light receiving member for use in electrophotography with aiming at heightening the photosensitivity and dark resistance, there are often observed a residual potential on the conventional light receiving member upon the use, and when it is repeatedly used for a long period of time, fatigue due to the repeated use will be accumulated to cause the so-called ghost phenomena inviting residual images.
Further, in the preparation of the light receiving layer of the conventional light receiving member for use in electrophotography using an A-Si material, hydrogen atoms, halogen atoms such as fluorine atoms or chlorine atoms, elements for controlling the electrical conduction type such as boron atoms or phosphorus atoms, or other kinds of atoms for improving the characteristics are selectively incorporated in the light receiving layer.
However, the resulting light receiving layer sometimes is accompanied with defects on electrical characteristics, photoconductive characteristics and/or breakdown voltage resistance depending upon the way the constituents to are employed.
That is, in the case of using the light receiving member having such light receiving layer, there often occur problems that the life of a photocarrier generated in the layer upon irradiation of light is not sufficient, inhibition of a charge injection from the side of the substrate in a dark layer region is not sufficiently carried out, and image defects likely due to a local breakdown phenomenon which is so-called "white oval marks on half-tone copies" or other image defects likely due to abrasion upon using a blade for the cleaning which is so-called "white line" are apt to appear on the transferred images on a paper sheet.
Further, in the case where the above light receiving member is used in a very moist atmosphere, or in the case where after being placed in that atmosphere it is used, the so-called "image flow" sometimes appears on the transferred images on a paper sheet.
In consequence, it is necessary to make further improvements not only in an A-Si material itself but also in the layer constitution, chemical composition for each constituent layer and preparation method in order to overcome the foregoing problems.